I have never seen this before Lisa. If yucca ( of any sort ) are common in your region, dont worry about getting rid of your problem. they will find new host yucca plants. My only problem is the brown spot fungus that gets on yuccas here and hard to control. A good source for keeping insects away is the Bayer tree and shrub insect spray. It is a systemic but a spoon full in a gallon of water makes a great spray and even holds up during a shower or two and effectively eliminates all insects and bugs with a clear appearance and this stuff works great for me on any plant. Good Luck Lisa.